One of the many design challenges in the field of spacecraft technology involves the protection of the spacecraft (e.g., communications satellites, space stations, etc.) from impact with micrometeoroids and orbital debris (MMOD). Typically, a spacecraft is likely to encounter numerous MMOD during a mission, and it has been projected by some scientists that orbital debris related to artificial objects is likely to increase by approximately 2 to 5 percent per year. The MMOD may approach a spacecraft at a hyper-velocity, e.g., in the range of approximately 10 to 20 km/sec. (as compared to the sonic velocity in air of approximately 0.3 km/sec.), and can cause serious damage to an unprotected spacecraft. Therefore, some type of protective shield against the threat of MMOD is generally implemented on the vulnerable areas of a spacecraft to protect it from this kind of damage.
Various types of mechanical shields (e.g., all-aluminum shields) have been developed to provide MMOD protection for a spacecraft. One type of shield commonly used for this purpose, generally known as the Whipple shield, consists basically of an outer aluminum wall and an inner aluminum wall enclosing a multi-layer material in a sandwich configuration. The multi-layer material is typically selected for thermal insulating and/or shock dispersion properties, and is generally fabricated from metal foils or ceramic fabrics. The outer wall of a Whipple shield is typically separated from the structure being protected by a standoff distance. This standoff distance is intended to defocus and spread the impact shock and impact debris over a relatively large area upon impacting the protected surface.
All-aluminum or Whipple types of protective shields, however, can impose a significant weight penalty on a protected structure, which is generally undesirable in a spacecraft application. In addition, the standoff distance of a Whipple shield typically becomes a vacuum space during a spacecraft mission, and when disposed on heat dissipation surfaces, can significantly lower the temperature on the outer surface of the shield. As the shield surface radiates at lower temperatures, the heat rejection efficiency of the protected heat dissipation surfaces of the spacecraft can be reduced substantially.
Accordingly, it is desirable to provide an MMOD protective device that is relatively lightweight in comparison to a typical all-aluminum or Whipple shield. In addition, it is desirable to provide an MMOD protective device that does not significantly compromise the heat dissipation capabilities of the protected structure. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.